This application is an application for patent which relates to air intake systems for internal combustion engines, particularly internal combustion engines for automobiles. More particularly, it relates to intake manifolds and air assist rails and methods for making the same.
Fuel injectors are often designed to use air under pressure to assist the atomization of fuel by the injectors. Since each injector in an engine requires air assist, each injector is connected to a supply of pressurized air.
Traditionally, since the injectors are in predetermined positions with respect to each other, the air is supplied to a bank of injectors by an external pod or rail. This pod is rigid and is attached to a row of injectors along a single bank. Thus, for in-line engines, there would be a single pod that extends the length of the engine connecting to all the cylinders. For engines with two banks of cylinders, such as xe2x80x9cVxe2x80x9d-type engines or horizontally opposed pancake engines, two pods are provided where each pod is connected to the injectors for a single bank of cylinders. In another arrangement, the air assist passageway is not provided by an external pod, but is formed as a passageway internal to the intake manifold.
While the external pod requires additional piping and connections for each of the injectors, it also permits a passageway with optimum air pressure and air distribution. It also permits the intake manifold and cylinder head geometry to be kept simple.
Air assist passageways formed internal to the manifold are significantly constrained in their design. For example, they are either molded using pins, or are formed by gun-drilling the manifold after it is molded. As a result, the air assist passageways typically have a circular cross section with a relatively constant cross sectional area, and a straight longitudinal axis. Their diameter is typically limited to fit between and around the injector pockets and the air induction ports for each cylinder. The longitudinal axes of the air assist passageways formed in the manifold are typically offset to one side of the fuel injector pockets such that they intersect the air injector pockets on one side.
These constraints cause several problems. First, there are significant air assist pressure drops from injector to injector as the assist air travels the length of the air assist passageway. Second, when the injectors operate, they generate pressure pulses that travel down the air assist passageways. Depending upon the geometry of the air assist passageways, these pressure pulses may cause injectors to be starved for assist air, or alternatively have too much assist air applied to the injectors. This is commonly called xe2x80x9ccross-talkxe2x80x9d between injectors and negatively affects the atomization of the fuel. In addition, fuel from an upstream injector can be introduced into the air assist passageways and can be transmitted to neighboring air injectors.
The problems are compounded by supplying assist air to an end of the internal air assist passageway. Typically, a connection is provided on one end of the air assist passageway into which the assist air is supplied. Thus, for example, the air assist passageways on a V-8 engine (having two banks of four cylinders) would be fed from an air line connected to an end of the air assist passageway. To reach the fuel injector at the far end of the engine, the passageway would have to pass three fuel injectors, all of them introducing pressure pulsations into the system that would affect the end cylinder. In a straight six-cylinder engine, the air assist passageway would pass five fuel injectors before reaching the last fuel injector in the bank of cylinders. Five fuel injectors introduce their pressure pulsations into the air assist passageway that would affect that last fuel injector.
What is needed therefore is an improved method and apparatus for supplying assist air to an engine having a plurality of fuel injectors. It is an object of this invention to provide such an apparatus and method.
In accordance with a first embodiment, an air intake system for an internal combustion engine having at least one bank of cylinders adjacent to each other is provided, including a first plurality of air induction passageways couplable to the at least one bank of cylinders for conducting combustion air to the cylinders in the first bank of cylinders, a first plurality of fuel injector pockets, each fluidly coupled with one of the first plurality of air induction passageways, and a first air assist passageway fluidly coupled with the first plurality of fuel injector pockets to communicate assist air to each of the fuel injector pockets, wherein the first air assist passageway has a first assist air feed port for receiving assist air and the first assist air port is disposed between at least two of the first plurality of fuel injector pockets.
The air intake system may also include a second plurality of air induction passageways couplable to at least another bank of cylinders of the internal combustion engine for conducting combustion air to the cylinders in the second bank of cylinders, a second plurality of fuel injector pockets, each fluidly coupled with one of the second plurality of air induction passageways, and a second air assist passageway fluidly coupled with the first plurality of fuel injector pockets to communicate assist air to each of the fuel injector pockets, wherein the air assist passageway has a second assist air feed port for receiving assist air and the second assist air port is disposed between at least two of the second plurality of fuel injector pockets.
The first and second pluralities of air induction passageways may each include at least three passageways, each of the at least three passageways being couplable to a corresponding cylinder of the first and second banks of cylinders, respectively.
The first and second pluralities of air induction passageways may each include at least four passageways, each of the at least four passageways being couplable to a corresponding cylinder of the first and second banks of cylinders, respectively.
The first plurality of air induction passageways may include at least four passageways, each of the at least four passageways being couplable to a corresponding cylinder of the first bank of cylinders.
The first plurality of injector pockets, the first plurality of air induction passageways, the first air assist passageway and the first assist air feed port may be formed in an intake manifold.
The first plurality of fuel injector pockets may have central longitudinal axes, and those axes may be intersected by the first air assist passageway.
The first air assist passageway may have a longitudinal axis, and that axis may substantially intersect the first longitudinal axes of the first plurality of fuel injector pockets.
The first air assist passageway may intersect the plurality of fuel injector pockets between two circumferential seats on each of the plurality of fuel injector pockets, and the two circumferential seats may be engageable with two flexible seals disposable between the two circumferential seats and a fuel injector.
The two flexible seals may be O-rings. The manifold may include a plenum, and may be made of fiber-reinforced plastic.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.